With the image retrieval technology, it is possible to determine whether a target image includes one or more images in an image library. In the mage retrieval technology, two steps are included: off-line training step and on-line retrieval step. In the off-line training step, at least one visual feature of each of the images in the image library is extracted to form an image feature index library. In the on-line retrieval step, the at least one visual feature of the target image is extracted and compared with that of each of images in the image feature index library to determine, from the image library, one or more reference images with a high similarity to the target image. In a case that each of the one or more reference images as determined has a similarity that is greater than a threshold with the target image, the target image may be considered to include the one or more reference images.
According to the entity for implementing the image retrieval technology, there may be cloud image retrieval and local image retrieval. In the cloud image retrieval, the target image is uploaded to the cloud, an image feature of the target image is compared with that of an image in the image library in the cloud, and a comparing result is transmitted to a mobile terminal. In the local image retrieval, firstly a feature library of a reference image data set is transmitted from the cloud to the mobile terminal, and the feature comparing is performed on the mobile terminal to obtain a comparing result.
In a case that illumination conditions are changed, an image is blurred due to the quick movement of a mobile terminal, or an effective object has a small occupation in the target image, the recognition accuracy of the existing image retrieval technology would be low, and a recognition error often occurs, which seriously affects the user experience.